1. Field of the Invention
The present invention relate to a partial discharging-resistant wire enamel composition and a partial discharging-resistant magnet wire.
2. Description of the Related Art
A mechanism of partial discharging deterioration of electrically insulation materials is hypothesized that charged particles generated by partial discharge collide with an insulation material, the collision causes cutting off of a polymer chain of the insulation material, and thermal decomposition due to sputtering and local temperature rise, further, ozone generated by the partial discharge causes chemical deterioration and the like of the insulation material, and progress of these deteriorations leads finally to insulation breakdown of an electric machinery coil.
Partial discharge deterioration in an inverter control apparatus which recently become to be used widely is presumed to be caused by a phenomenon in which a high voltage surge is superimposed as a switch pulse, leading to deterioration of a coil of an inverter control apparatus.
Contrary to this, partial discharge deterioration in an generally used high voltage transformer treated with mold insulation or interlayer insulation is caused by minute cavity generated in an insulation layer.
As the insulation material which is not easily deteriorated by partial discharge, inorganic insulation materials, such as metal oxides, nitrides, glass, mica and the like are known.
Further, as the magnet wire having excellent partial discharge deterioration-resistance, those produced by coating wire enamel composition prepared by dispersing an inorganic insulation material fine powder, such as silica, alumina, titanium oxide and the like are known.
In such a partial discharge-resistant magnet wire, the lager the containing amount of inorganic insulation material fine powder in an insulation coating, the greater the improvement of partial discharge deterioration-resistance.
However, in a magnet wire containing a large amount of an inorganic insulation material fine powder in an insulation coating, flexibility, softening property, winding property, extensibility and the like deteriorate. If an electric machinery coil is formed by a magnet wire having deteriorated flexibility, softening property, winding property, extensibility and the like, many cracks will be formed in a coating of the magnet wire. Consequently, an effect of improving partial discharge deterioration-resistance can not be exerted.
An inorganic insulation material-dispersed magnet wire having a multi-layer structure is used for satisfying both improvement in partial discharge deterioration-resistance and improvement in flexibility, softening property, winding property, extensibility and the like.
FIGS. 1 and 2 show a cross sectional view of such an inorganic insulation material-dispersed magnet wire having a multi-layer structure. In FIGS. 1 and 2, 1 represents a conductor, 2 represents a polyamideimide under coating layer, 3 represents an inorganic insulation material-dispersed wire enamel composition coating layer, and 4 represents a polyamideimide over coating layer.
An inorganic insulation material-dispersed magnet wire having a multi-layer structure as shown in FIG. 1 is comprising a conductor 1, an inorganic insulation material-dispersed wire enamel composition coating layer 3 provided on a conductor 1, and a polyamideimide over coating layer 4 provided on the inorganic insulation material-dispersed wire enamel composition coating layer 3.
An inorganic insulation material-dispersed magnet wire having a multi-layer structure as shown in FIG. 2 is comprising a conductor 1, a polyamideimide under coating layer 2 provided on a conductor 1, an inorganic insulation material-dispersed wire enamel composition coating layer 3 provided on the polyamideimide under coating layer 2, and a polyamideimide over coating layer 4 provided on the inorganic insulation material-dispersed wire enamel composition coating layer 3.
However, in the above-described magnet wire as shown in FIG. 1 and FIG. 2, a large amount of inorganic insulation material is dispersed in the inorganic insulation material-dispersed wire enamel composition coating layer 3, consequently, flexibility, softening property, winding property, extensibility and the like are inevitably inferior to those of a general enameled wire. For example, if these magnet wires are wound after 10% extension, cracks are formed on the inorganic insulation material-dispersed wire enamel composition coating layer 3.
Further, in a wire enamel composition in which a large amount of an inorganic insulation material has thus been dispersed, as a result of precipitation or whitening of the inorganic insulation material, there appears a fear of deterioration in surface smoothness of a magnet wire, or decrease in electric insulation-resistance and mechanical properties.
The present invention has been made based on the above-mentioned problems, and an object thereof is to solve the above-mentioned prior art problems and to provide a partial discharge-resistant wire enamel composition having excellent dispersibility of an inorganic insulation material and a partial discharge-resistant magnet wire having both flexibility and partial discharge deterioration-resistance.
A partial discharge-resistant wire enamel composition of the present invention is a wire enamel composition wherein at least one fine particle sol selected from the group of metal oxide fine particle sol and silicon oxide fine particle sol is dispersed, said wire enamel composition comprising 100 parts by weight of wire enamel resin and 3 to 100 part by weight of at least one fine particle selected from the group of a metal oxide fine particle and a silicon oxide fine particle.
Further, a partial discharge-resistant magnet wire of the present invention is a magnet wire obtained by coating and baking directly or through other coating layer on a conductor a partial discharge-resistant wire enamel composition wherein at least one fine particle sol selected from the group of metal oxide fine particle sol and silicon oxide fine particle sol is dispersed, said wire enamel composition comprising 100 parts by weight of wire enamel resin and 3 to 100 parts by weight of at least one fine particle selected from the group of a metal oxide fine particle and a silicon oxide fine particle.
In the present invention, the content of fine particle selected form the group of a metal oxide fine particle and a silicon oxide fine particle is from 3 to 100 parts by weight per 100 parts by weight of wire enamel resin content of a wire enamel composition. If the content is less than 3 parts by weight, an effect of improving partial discharge deterioration will be insufficient, and if over 100 parts by weight, flexibility and extension-resistance will be deteriorate.
The future of the present invention is that a transparent or opalescent colloid (this colloid is referred to as sol) comprising dispersing medium having excellent compatibility with a wire enamel composition and at least one fine particle selected from the group of a metal oxide fine particular and a silicon oxide tin particle dispersed therein, is dispersed in a wire enamel composition to accomplish a uniform dispersion of a fine particle. In this case, use of a metal oxide fine particle or a silicon oxide fine particle having an average particle size of 100 nm (100xc3x9710xe2x88x926 mm) or less is preferable for realizing smoothness or flexibility of the wire enamel composition coating layer.
In the magnet wire of the present invention, a coating layer composed of a wire enamel composition in which at least one fine particle sol selected from the group of metal oxide fine particle sol and silicon oxide fine particle sol is dispersed may be formed as the outermost layer. Another aspect of the magnet wire of this invention is lubricant coating layer which import excellent sliding property to a magnet wire may be formed around the coating layer composed of a wire enamel composition of this invention.